Speakerphone with a novel loudspeaker placement

ABSTRACT

A new speakerphone wherein a loudspeaker is oriented to face the listeners of an audio conference is disclosed. New speakerphones which have a bass loudspeaker and at least one tweeter loudspeaker wherein the tweeter loudspeaker is oriented towards listeners of an audio conference are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/136,137, filed May 24, 2005, now U.S. Pat. No. ______, which isincorporated by reference herein. U.S. patent application Ser. No.11/136,137 is related to a patent application assigned to the sameassignee, titled “Integrated Desktop Videoconferencing Phone,” byTimothy Root, Tony Duys, and Dan Phelps, Docket No. 199-0265US, filed onApr. 15, 2005, which is incorporated by reference herein and to patentapplication Ser. No. 10/412,755, Docket No. 199-0016US, filed on Apr.11, 2003, titled “Portable Videoconference System,” which is alsoincorporated by reference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a speakerphone, more specifically to novel wayof placing loudspeakers in a speakerphone to improve the intelligibilityof speech of conference talker.

2. Description of the Related Art

Teleconferencing has long been an essential tool for communication inbusiness, government and educational institutions. There are many typesof teleconferencing equipment based on many characterizations. One typeof teleconferencing unit is a video conference unit 100 as shown in FIG.1, which transmits real-time video images as well as real-time audiosignals. A video conferencing unit 100 typically comprises a videoprocessing component and an audio processing component. The videoprocessing component may include a camera 102 to pick up live images ofconference participants and a video display 130 for showing real-timevideo images of conference participants or images of documents. Theaudio portion of the video conferencing unit 100 typically includes oneor more microphones 145 and 155 connected to a processor 110 throughwires 156 and 157 to pick up voice signals of conference participants,and loudspeakers 122 and 124 to reproduce voices of the participants atthe far end. The processor 110 is connected to the far side of theconference through a cable 150. The processor 110 may control theoperation of the video conference unit 100 and perform any the dataprocessing necessary during operation.

Another type of teleconference unit is an audio conference unit, whichis typically a speakerphone or a simple telephone that includes at leasta loudspeaker and a microphone. FIGS. 2 a-2 c illustrate a few examplesof speakerphones. A speakerphone can be viewed as essentially a videoconference unit without the video capability and the video-relatedhardware and network supporting infrastructure. To make an audio-onlyconference call using a speakerphone is much simpler and easier thanusing a videoconference unit. A speakerphone is typically much cheaperthan a videoconference unit. An analog telephone is typically thecheapest, simplest and easiest to use teleconference unit.

FIG. 2 a shows a typical speakerphone 200, for example, a PolycomVTX-1000 speakerphone which is commercially available from the assigneeof the current patent application. The speakerphone 200 has severalmicrophones 242, 244 and 246, a loudspeaker 222 and a control module260. The control module 260 has a controller (not shown) that is coupledto the loudspeakers, microphones and network interface (not shown). Thecontrol module also has two keyboards 270 and 272 and a display screen262. A cable 250 coupled to the network interface (not shown) providespower and network connections. FIGS. 2 b and 2 c show a slightlydifferent speakerphone 210, which has similar components includingmicrophones 212, 214 and 216, loudspeaker 222 and a control module 220.In speakerphone 210, the components are arranged in a slightly differentphysical configuration compared to the speakerphone 200. FIG. 2 b showsa top view and FIG. 2 c shows a side view of the speakerphone 210.

The low cost of a speakerphone is often associated with the low audioquality of the speakerphone. It is common that when several peopleparticipate in a conference call, it may be difficult to understand whata talker on the far end is talking about even if the volume of thespeakerphone is turned on high. The conference call participants at thenear end may have to sit very close to the speakerphone to be able tohear and understand the far end talker. This makes the participants tocrowd over the speakerphone, even though there is plenty of space in theconference room. This makes the conference very uncomfortable andinconvenient.

The problem associated with the difficulty of understanding the talkersat a far end site when there are several people on both conference sitesdoes not appear to be solved by turning up the volume on thespeakerphone. Such problem does not appear to be present in many videoconference units, which are substantially more expensive.

It is desirable to have a method and a speakerphone with improved soundquality without incurring the substantial cost of a videoconferenceunit.

BRIEF SUMMARY OF THE INVENTION

In one embodiment of the current invention, the orientation ofloudspeakers in a speakerphone is changed from facing upward verticallyto facing conference participants (listeners) horizontally. This way,the sound reproduced by the loudspeakers can reach the conferenceparticipants directly.

In some other embodiments of the current invention, multipleloudspeakers are installed in a speakerphone, wherein a bass loudspeakeris used to reproduce low frequency sound, and at least one small tweeterloudspeaker is used to reproduce high frequency sound. The tweeterloudspeaker is oriented towards the listeners in an audio conference,rather than the usual orientation which is towards the ceiling of theconference room. Multiple tweeter loudspeakers may be installed suchthat there are direct sound waves coming from a tweeter loudspeakertowards each listener sitting around the conference table. The smallsize of a tweeter loudspeaker makes it easy to orient to its optimumdirection individually without affecting the overall size or profile ofthe speakerphone. The low cost of a tweeter loudspeaker does notincrease the cost of the overall speakerphone.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

A better understanding of the invention can be had when the followingdetailed description of the preferred embodiments is considered inconjunction with the following drawings, in which:

FIG. 1 depicts a typical video conferencing unit in prior art.

FIGS. 2 a-2 c depict speakerphones in prior art.

FIGS. 3 a and 3 b illustrate the traveling patterns of sound waves ofhigh frequencies and of low frequencies respectively.

FIGS. 4 a and 4 b depict one embodiment of the current invention.

FIGS. 5 a, 5 b, 6 a and 6 b depict several other embodiments of thecurrent invention.

DETAILED DESCRIPTION OF THE INVENTION

During the investigation of improving the sound quality ofspeakerphones, the inventors of the current invention discovered thatthe material qualities of microphones or loudspeakers are not the majorcontributors to the low sound quality of speakerphones. When comparingthe loudspeakers in a typical video conference unit and the loudspeakerin a high quality speakerphone, the quality of the loudspeakersthemselves is comparable. Still, it is very difficult to understand thespeech of far end talker using a speakerphone, if the listener is onlyslightly away from the speakerphone, e.g. sitting at a large conferencetable. It is also noticed that if the listener is standing and leaningright above the loudspeaker of the speakerphone, the intelligibilityincreases substantially. It is discovered that the intelligibilitydifferences between a typical speakerphone and a typical videoconference unit is more related to the placement and orientation of theloudspeakers in respective units. As shown in FIG. 1, the loudspeakers122 and 124 of a video conference system are typically installed facingthe listeners in a conference room. On the other hand, as illustrated inFIGS. 3 a and 3 b, the loudspeaker 310 in a speakerphone is typicallyoriented upward, facing the ceiling of the conference room.

As shown in FIGS. 3 a and 3 b, a loudspeaker 310 has a center line 342,which is a line perpendicular to the surface of the loudspeaker. Acenter line direction is the direction that is perpendicular to thesurface of the loudspeaker and away from the center of the loudspeaker.A center line angle is the angle between the center line and thehorizontal direction. In speakerphones, the center line angles of theloudspeakers are about 90 degrees, i.e. in a vertically upwarddirection, while in many video conference units, the center line anglesare about 0 degree, i.e. in a horizontal direction. In most videoconference units, e.g. in video conference unit 100 shown in FIG. 1, theloudspeakers (e.g. 122 and 124) are the loudspeakers in a TV monitor130, which is external to the video conference module 110. The videoconference module 110 is the box that contains the network connection,the camera, the microphones and the data processing component.

FIG. 3 a illustrates the sound wave traveling pattern for high frequencysound wave, e.g. sound with frequencies above 1000 Hz. A speakerphone320 is placed on a conference table 304. The loudspeaker 310 in thespeakerphone 320 is facing upward towards the ceiling 302 of theconference room. As for the high frequency waves 342, 332 and 352, thesound wave field is narrow. They are traveling upward towards theceiling. Some of the sound waves 344 and 354 are reflected by theceiling 302, and then reach the listeners 312 and 314. The listeners 312and 314 do not actually hear the sound coming from the loudspeaker 310directly. On the other hand, FIG. 3 b illustrates the sound wavetraveling pattern for low frequency sound waves, e.g. sound withfrequencies below 1000 Hz. The low frequency sound waves are typicallyless localized. So even coming from the same loudspeaker 310, some ofthe sound waves 362 and 364 can reach the listeners 312 and 314directly, besides the indirect sound waves 344, 354 etc. Those lowfrequency sound waves can carry much of the energy coming out of theloudspeaker 310 that can reach the listeners. When increasing the volumeof the loudspeakers 310, the low frequency amplitude is increasedaccordingly. But the high frequency portion of the sound waves does notincrease proportionately because the majority of the increased energy inthe high frequency waves is dissipated in the conference room beforereaching the listeners. This makes the audio spectrum heard by thelisteners more heavily weighted in the low frequency spectrum. It isknown that most of the audio information is carried by high frequencyportion of the audio spectrum. Missing the high frequency portion of theaudio spectrum makes the speech less intelligible. Increasing theloudspeaker volume only makes the sound heard by the listeners moreover-weighted at the low frequency spectrum. This is a reason whyincreasing the volume of the loudspeaker in a speakerphone does notincrease necessarily the intelligibility of the talkers from the far endof the conference call.

For a typical round loudspeaker, the angular coverage is about 60degrees or 90 degrees for larger ones. As illustrated in FIG. 3 a, theangle between lines 342 and 352 is typically less than 60 degree forfull bandwidth. For low frequency sound, the angular coverage may begreater, but that sound is not very intelligible due to the excess lossof high frequency components. Therefore, measuring from horizontaldirection, a listener needs to be at or above at least 60 (or 45 forlarger ones) degree to be within the full spectrum sound field of theloudspeaker. As shown in FIG. 3 a, the listener's ears need to be abovethe lines 352 and 342, which are about 60 degrees above horizon.

But in a typical conference setting, listeners' ears are typically belowsuch level. In a typical audio conference, participants are usuallysitting around a conference table. The ear level of participants for anaverage person is about 18″ above the conference table level which is atabout 29″ above ground. That is for an average person, his ears areabout 47″ above ground when he is sitting. For a typical conferencetable, 48″×120″, the angle between the ear level to horizontal directioncentered at the loudspeaker of a speakerphone placed at the center ofthe conference table is about 17 degree (at the far end of theconference table, arctan(18/60)=17 degrees) to about 37 degree (at thecenter of conference table, arctan(18/24)=37 degrees). So for an averageperson sitting at the center of the conference table near thespeakerphone, he is still not within the full-spectrum sound field ofthe loudspeaker.

If a person is standing, the ear level is about 36″ above the table, or65″ above ground. The corresponding angles are about 31 and 56 degrees.So if the person is standing near the center of the conference table, heis within the full-spectrum sound field and can have goodintelligibility. If he is standing a little further away from thecenter, he may need to lean over the table to get the sameintelligibility.

To correct the problems, according to the embodiments of the currentinvention, the loudspeaker orientation in a speakerphone is changed.Rather than facing the ceiling, the loudspeakers in speakerphonesaccording to some embodiments of current invention are oriented towardsthe listeners in a conference room. The loudspeakers in a speakerphoneare facing near horizontal, i.e. the center line angle is near 0 degree,rather than vertically upwards, i.e. the center line angle is at 90degrees.

FIGS. 4 a and 4 b illustrate one embodiment of the current invention.FIG. 4 a is a side view and FIG. 4 b is a top view. The speakerphone 420is similar to the speakerphone 210 depicted in FIGS. 2 b and 2 c, exceptthat loudspeakers 422 and 424 replace the single loudspeaker 222 as inspeakerphone 210. Similar to the speakerphone 210, almost allcomponents, including microphones (not shown), loudspeakers 422 and 424,a processor and a network interface (not shown) are contained within thespeakerphone 210. The speakerphone is a self-contained device. Theloudspeaker 422 is facing listener 412 and the loudspeaker 424 is facinglistener 414. The center line 434 (432) of the loudspeaker 424 (422) isat about 30 degrees from horizontal, such that the sound angularcoverage is from horizontal (0 degree) to 60 degrees above horizontalfor a loudspeaker with 60 degree angular coverage. To provide betterroom coverage, loudspeakers 424 and 422 are directed to differentdirections in the horizontal plane. More specifically, the center lines432 and 434 are not in parallel, or the angle between the two is greaterthan 0 degree. In this example, the angle between the two center lines434 and 432 is about 180 degrees. Listeners are within the full spectrumcoverage, i.e. most of the sound waves from the loudspeakers go to thelisteners directly. The sound waves the listeners hear are more balancedand complete, rather than over-weighted at the low frequencies. In thisembodiment, the loudspeakers 422 and 424 are identical. They are fullspectrum loudspeakers, i.e. each loudspeaker reproduces both lowfrequency and high frequency audio. Depending on the property of theloudspeakers used in a speakerphone, the center line angle is typicallybetween 0 degree (i.e. horizontal) and 45 degrees (i.e. half way betweenvertical and horizontal). When the center line angle is set at 45degree, if the loudspeaker has a 90 degree angular coverage, then theentire range of 0 degree to 90 degrees is covered by the loudspeaker.

FIGS. 4 c and 4 d illustrate a simplified version of the embodimentshown in FIGS. 4 a and 4 b. In this embodiment, there is only oneloudspeaker 464 installed in a raised a loudspeaker tower 462 in aspeakerphone 460. The loudspeaker 464 is facing the listener 414, in ahorizontal direction, i.e. the center line angle at 0 degree. Theforward sound 494 produced by loudspeaker 464 can reach the listener 414directly. The optional front sound duct and opening 495 helps in guidingthe sound waves. In one implementation, the center of the loudspeaker isabout 4″ above conference table. So the sound field is from horizon aslimited by the conference table to about 30 degrees above horizontal.Using the same example as discussed above, the ear level for a personsitting at the center of the conference table is arctan((18−4)/24)=30degree. The angle of the ear level for persons sitting further away fromthe center is less than 30 degrees. So even using a loudspeaker withonly 60 degree angular coverage, there is sufficient vertical angularcoverage.

The listener 412 who is sitting facing the back of the speakerphone 460may not have as good quality sound as the listener 414 who is sitting inthe front of the speakerphone 460, but listener 412 can still get somedirect sound waves from the loudspeaker 464. The optional back soundduct 493 may help directing the sound. The sound quality in the back ofa loudspeaker is still better than that of the sound that is 90 degreesto the loudspeaker, which is the sound heard by listeners using priorart speakerphones. The speakerphone 460 may also have a dial-pad 472.Due to the simplicity, this speakerphone is suitable for use in a smallconference where people sit either in front of the speakerphone orfacing its back. If a loudspeaker with broad angular coverage is used insuch a speakerphone, then horizontal angular coverage may be furtherimproved.

To further improve the sound quality and configuration flexibility,FIGS. 5 a , 5 b, 6 a and 6 b illustrate some alternative embodiments ofthe current invention where separate tweeter and bass loudspeakers areused. The embodiment shown in FIGS. 5 a and 5 b is very similar to theone shown in FIGS. 4 a and 4 b except for the addition of a bassloudspeaker 528. The addition of the bass loudspeaker 528 makes itpossible to replace the full spectrum loudspeakers 422 and 424 as inspeakerphone 420 with tweeter loudspeakers 521, 522, 523 and 524 as inspeakerphone 520. The tweeter loudspeakers 521-524 are much smaller thanthe full spectrum loudspeakers 422 and 424. They are typically muchcheaper also. The smaller sized make the tweeter loudspeakers 521-524much easier to orient towards the listeners 512 and 514 etc. Eachtweeter loudspeaker 521-524 has a center line 531-534 respectively. Ifthe tweeter loudspeakers 521-524 have the same audio properties, then itis desirable to place them evenly within the speakerphone, i.e. have theangles between any two neighboring center lines be substantially thesame. In this example, the angles between any two neighboring centerlines are all 90 degrees, e.g. angles between lines 531 and 532, 531 and534, 532 and 533, and 533 and 534 are all 90 degrees. It is alsopossible to add more of these tweeter loudspeakers to cover more spacesaround the conference table if necessary. Obviously, if differentnumbers of loudspeakers are used in a speakerphone, then the anglesbetween the neighboring loudspeakers are different. If the audioproperties (e.g. angular coverage) of the loudspeakers used aredifferent, then the angles between the neighboring loudspeakers are alsodifferent. The separation of the reproduction of bass frequencies andtweeter frequencies with different loudspeakers improves the soundquality of the speakerphone. The direct sound waves, more importantlythe direct high frequency sound waves towards the listener, alsoincrease the intelligibility greatly with minimum cost. The center lineangle of the bass loudspeaker 528 is at about 90 degrees, while those ofthe tweeter loudspeakers 521-524 are between 0-45 degrees, typically atabout 15 degrees.

Due to the small size of the tweeter loudspeakers, they can be orientedat any directions necessary, without increasing the overall profile(height) of a speakerphone, such as in the embodiment shown in FIGS. 6 aand 6 b. The speakerphone 600 is about the same height as the one shownin FIG. 2 a. The speakerphone 600 in the example shown in FIGS. 6 a and6 b is placed on a conference table 604 and facing upward towards theceiling 602. It has one bass loudspeaker 628, several small tweeterloudspeakers 622 and 624 and several microphones 613 and 615(loudspeaker 626 and microphone 617 are not shown in FIG. 6 a but areshown in FIG. 6 b). The bass loudspeaker 628 is facing downward, i.e.with a center line angle at −90 degrees. The low frequency sound 646 isreflected by the conference table 604 and then radiates towards thelisteners 612 and 614. The high frequency sound waves 642 and 644generated by the tweeter loudspeakers 622, 624 and 626 etc. travelingdirectly towards the listeners 612 and 614. The center line angles ofthe tweeter loudspeakers, e.g. center line 645, are at about 30 degreesfor the embodiment as shown in FIG. 6 a. The low frequency waves 646 arenot directional, so the orientation of the bass loudspeaker 628 is notimportant. It can be place anywhere with any orientation, i.e. from −90degree to +90 degrees, in the speakerphone 600 that is convenient forother reasons. The tweeter loudspeakers 622, 624 and 626 may be placedat the three corners of the speakerphone, facing the listeners.

In the above embodiments, the loudspeaker orientations are fixed, butthey do not have to be. If desired, the loudspeaker orientations can beadjusted based on the conference situation. For example, the tweeterloudspeakers 622, 624 and 626 may be adjusted during use in a conferencecall to make their orientations optimum for the particular conferencecall. Some of them may be directed more upward to taller people or whoare standing, others may stay at their original positions, directing topeople sitting at the conference table.

As discussed above, the current invention discloses a reason for poorsound quality, i.e. poor intelligibility, of a speakerphone. Utilizingthis finding, the embodiments of the current invention change thestructures of typical speakerphones slightly but improving the soundquality greatly. The better orientations of the loudspeakers inspeakerphones according to the embodiments of the current inventiongreatly improve the intelligibility of talkers of the far end of aconference call. Most embodiments of the current invention can also saveenergies because less sound energy is wasted due to room dissipation.The separation of audio spectrum reproduction also further improves thesound quality and the flexibility of speakerphone construction.Furthermore, unlike a typical video conference unit which is place atone end of a conference room, where the people can only sit in front ofit, in an audio conference call, a speakerphone is placed at the centerof the conference room on a conference table, where people sit aroundthe speakerphone. Using a speakerphone, people sitting around the tablecan all hear the speech of talkers at the far end of the conferencecall.

While illustrative embodiments of the invention have been illustratedand described, it will be appreciated that various changes can be madetherein without departing from the spirit and scope of the invention.

1. A speakerphone for placement on a horizontal surface comprising: amicrophone; a plurality of loudspeakers, each loudspeaker facingupwardly and each loudspeaker having a center line angle, wherein thecenter line angle is at most 45 degrees above horizontal and the anglebetween any two neighboring loudspeaker center lines is greater than 0degrees; an interface through which the speakerphone is connected withanother teleconference unit; a process unit coupled to the microphone,the loudspeakers and the interface; and a housing containing themicrophone, the loudspeakers, the interface and the process unit.
 2. Thespeakerphone of claim 1, wherein at least one loudspeaker center lineangle is adjustable up to at most 45 degrees above horizontal.
 3. Thespeakerphone of claim 1, further comprising: a bass loudspeaker coupledto the process unit, wherein the bass loudspeaker has a center lineangle, and wherein the plurality of loudspeakers are tweeterloudspeakers.
 4. The speakerphone of claim 3, wherein the center lineangle of the bass loudspeaker is between −90 degrees and 90 degrees fromhorizontal.
 5. The speakerphone of claim 4, wherein the center lineangle of the bass loudspeaker is −90 degrees from horizontal.
 6. Thespeakerphone of claim 1, further comprising: wherein the angle betweenany two neighboring loudspeakers' center lines is substantially the sameas the angle between any other two neighboring loudspeakers' centerlines.
 7. The speakerphone of claim 6, further comprising: one or moreadditional microphones coupled to the process unit.
 8. A speakerphonecomprising: a microphone; a loudspeaker having a center line angle,wherein the center line angle is at most 45 degrees above horizontal; aninterface through which the speakerphone is connected with anotherteleconference unit; a process unit coupled to the microphone, theloudspeaker and the interface; and a housing containing the microphone,the loudspeaker, the interface and the process unit, wherein the housinghas at least two openings, one opening in front of the loudspeaker andone at the back of the loudspeaker.
 9. A speakerphone operable to beplaced on a conference table in a conference room, wherein chairs areplaced around all sides of the conference table to accommodate seatedconference participants, the speakerphone comprising: a microphone; aloudspeaker having a center line, wherein the loudspeaker is oriented todeliver high frequency sound directly to a seated conferenceparticipant; an interface through which the speakerphone is connectedwith another teleconference unit; a process unit coupled to themicrophone, the first loudspeaker and the interface; and a housingcontaining the microphone, the loudspeaker, the interface and theprocess unit.
 10. The speakerphone of claim 9, further comprising: aplurality of loudspeakers having a center line coupled to the processunit, wherein each of the plurality of loudspeakers is oriented todeliver high frequency sound directly to a seated conferenceparticipant.
 11. The speakerphone of claim 9, further comprising: a bassloudspeaker coupled to the process unit, wherein the bass loudspeakerhas a center line angle; wherein the loudspeaker and the plurality ofloudspeakers are tweeter loudspeakers.
 12. The speakerphone of claim 11,wherein the center line angle of the bass loudspeaker is between −90degrees and 90 degrees from horizontal.
 13. The speakerphone of claim12, wherein the center line angle of the bass loudspeaker is −90 degreesfrom horizontal.